1. Field of the Invention
The present invention generally relates to hand guards for rifles, and more particularly to a quick-detach and free-floating forward hand guard assembly for a rifle that has no contact with the rifle's barrel and comprises a two-piece quad rail hand guard structure, including a top hand guard element engaged with, and extending forwardly from, an outer barrel nut in a laterally-stable cantilevered orientation, and also including a bottom hand guard element locked with the top hand guard element to remain free-floating therefrom. The top hand guard element slides over, and is solely supported by, the outer barrel nut, which is telescopically received over an inner barrel nut having fixed connection to a portion of the rifle's upper receiver, thus allowing the rifle's barrel (which also has an independent fixed connection to the rifle's receiver) to extend through the generally tubular inner barrel nut without any contact therewith. The outer barrel nut is longitudinally secured to the inner barrel nut with set screws to provide a fixed/non-rotational connection between them, which in combination with top/bottom stabilizing structure on the outer barrel nut that engages interior hand guard structure, prevents up-and-down or side-to-side hand guard movement and allows the cantilevered two-piece present invention hand guard to hold tight and true during use. The present invention further comprises plurality of venting holes through the top and bottom hand guard elements and an aluminum outer barrel nut configured with baffles for heat dissipation, with one embodiment that allows quick-detach barrel removal comprising a hinged outer barrel nut with clamshell action and an inner barrel nut with a two-piece separable extension that easily splits in two for quick removal while allowing its adjacent ring-shaped receiver end to remain secured to the upper receiver portion of the rifle. To achieve quick and easy installation, the top hand guard element has two upper female recesses in opposed positions that during installation allow it to slide on and around raised lugs on the left and right sides of the outer barrel nut with a downward push. Additional lower recesses about midway on the bottom hand guard element are configured to allow raised lugs on each side of the upper recesses to slide into them, and pushing the bottom hand guard element in an upward direction then allows it to slide in a backward motion that locks it to the top hand guard element and against the outer barrel nut approximately one inch forward of the back half of the outer barrel nut. A spring-loaded detent screw engaged with one sling swivel recess (having a rotation limiter and threads) that is located on the receiver end of the top hand guard element tightly secures the top and bottom hand guard elements together, and at the same time puts pressure on both sides of the present invention hand guard due to the fact that the tip of the spring detent is against the inner barrel nut pushing away from the opposite side of the barrel nut. What sets the present invention hand guard apart from all others is structure allowing unique assembly and disassembly, and the first 2.25-inches of the end closest to the receiver is where most of the mechanics take place. In addition, distinguishable structure in the present invention hand guard provides advantages during use in extreme environmental conditions, including desert, snow, and salt water, to aid heat dissipation generated during weapon operation and prevent shifts in barrel alignment over time that could adversely affect weapon accuracy.
2. Description of the Related Art
Gunstocks for handheld weapons date back to the sixteenth century and at that time typically comprised a simple stick fitted into a socket in the breech end of the weapon to provide a handle for the user. Over the following centuries, gunstocks typically remained fashioned from wood. Initially, gunstocks were one piece from butt to fore end, but certain weapon configurations lent themselves to two-piece stocks where the fore end was separate from the butt and grip.
The evolution of the rifle, and especially with respect to the genre of weapons categorized as assault rifles or assault weapons mass-produced for arming a country's military forces, has resulted in the use of gunstock hand guards that are separate from the remaining stock members, which facilitates cleaning. Furthermore, while traditional gunstocks have been machined from wooden blanks, today's gunstocks are typically formed of metal, injection molded thermoplastic, or a combination of the two.
Use of a separate gunstock hand guard is now common and fulfills multiple functions. The primary purpose of the hand guard is to insulate the shooter's hand from the heat of the rifle barrel. Secondly, the hand guard can include provisions (such as groove sets on one or more of its sides commonly referred to as a rail) for mounting accessories to the weapon such as, for example, a flashlight aligned with the barrel to illuminate the area in front of the weapon in low light or dark lighting conditions. On early rifles, accessory mounting provisions were almost exclusively employed for mounting telescopic sights and were thus provided mainly on the top portion of the rifle's receiver. However, for militarized assault rifles such as the M16, accessory mounting provisions are found on the hand guard (commonly known as Picatinny rails since they were developed at the Picatinny Arsenal), with one or more Picatinny rails usually found on each hand guard. Picatinny rails are standardized in structure, with dimensional specifications found in MIL-STD-1913 or ST ANAG 2324. As used herein, the term “quad rail” denotes four Picatinny rails placed equal lengths apart on a cylinder type hand guard. Hand guards may be either permanently mounted to the weapon or employ a “quick attach/detach” design that allows quick separation into two halves.
In prior art rifles, the barrel rests in contact with the stock and in particular with the fore end (or hand guard portion) of the stock. If the stock is manufactured of wood, environmental conditions or operational use may shift the alignment of the stock, which, in turn, may cause the attached barrel to slightly shift its alignment over time. This alignment shift can significantly alter the flight path of the projectile, and thus its impact point. Contact between the barrel and the stock also interferes with the natural frequency of the barrel, which, in some cases, can be detrimental on the weapon's accuracy. The interference of the stock with the barrel's forced oscillation as the projectile passes down the bore can cause the barrel to vibrate inconsistently from shot to shot, depending on differing external forces acting upon the stock at the time of the shot. Micro-vibrations acting during the projectile's passage through the barrel can result in unexpected trajectory differences as the projectile exits its bore, thus changing the downrange impact point.
One prior art method of minimizing this detrimental interference between the hand guard and the barrel has been to free-float the barrel with respect to the hand guard. Specifically, the barrel and the hand guard are each independently affixed to the weapon's receiver and project forward from the receiver in cantilevered fashion. The barrel and stock are designed to not touch at any point along the barrel's length. Thus, the barrel is “free-floating” and does not contact other gun parts, other than the weapon's front sight, which minimizes mechanical pressure distortions potentially affecting barrel alignment and further allows vibration to occur at the barrel's natural frequency. Free-floating hand guards have also been used. However, to maintain stability of the prior art free-floating hand guard, its attachment has typically been permanent, or comprised a one-piece quick-attach design to prevent the lateral shifting of hand guard elements with respect to each other that could otherwise be expected to occur in multiple-piece hand guards and potentially lead to weapon inaccuracy.
Another disadvantage of single piece hand guards is that, even if quickly detachable, they typically also require the highly undesirable removal of the front sight from the barrel in order to facilitate total removal of the hand guard for weapon cleaning. Conversely, quickly detachable hand guards comprising a multiple-piece (usually two pieces) design are not free-floating and instead are typically attached to the front end of the barrel. The inventor herein previously developed a two-piece hand guard having internal male ribs that went into female slots on the outer barrel nut (which is disclosed in U.S. patent application Ser. No. 13/106,357). The top hand guard element was installed in a downward push straight onto the outer barrel nut, and the bottom hand guard element was installed the same way only in the upward push direction. Latches were then used to secure the top and bottom hand guard elements together. Although these features allowed easy assembly, certain features made it too costly to manufacture. In contrast, the present invention hand guard disclosed herein has top and bottom hand guard elements without internal features that are costly to manufacture. In addition, the outer barrel nut structure in the present invention has no female rib features, instead having raised lugs on its left and right sides that allow the top hand guard element to slide on the outer barrel nut with the same downward push that the inventor herein used for the hand guard in his U.S. patent application Ser. No. 13/106,357. The improvement herein prevents a need for latches to connect the top and bottom hand guard elements together during use through use of a spring-loaded detent screw engaged with one sling swivel recess (having a rotation limiter and threads) that is located on the receiver end of the top hand guard element. The detent screw tightly secures the top and bottom hand guard elements together, and at the same time puts pressure on both sides of the present invention hand guard due to the fact that the tip of the spring detent is against the inner barrel nut pushing away from the opposite side of the barrel nut.
From the discussion hereinabove it can be determined that a two-piece and quick-detach quad rail hand guard for rifles is known, but none have structure allowing them to be free-floated. Two-piece and free-floated quad rail hand guards are also known, but none have a quick-detach construction. Furthermore, although one free-floated and quick-detach quad rail hand guard is known, it has a one-piece construction with undesired limitation that when there is an obstruction in front of the hand guard, such as a front sight or gas block, the hand guard cannot come off unless the sight or gas block is removed. The present invention hand guard herein has structure that addresses all four of the desired features in a hand guard. It is quick-detach, free-floated, quad rail, and two-piece, so that its top and bottom hand guard elements can quickly be removed to expose the barrel, yet its structure prevents up-and-down or side-to-side movement thereof during use, allowing the two-piece present invention hand guard to hold tight and true and not cause any adverse interference with weapon accuracy. No other hand guard on market does this, while also allowing quick attachment/detachment without removal of an attached scope or other rifle accessory and providing an option for quick-detach barrel removal when the hinged version of its outer barrel nut is used with the inner barrel nut having a separable two-piece extension.